Kritik Systems

Why it exists

Quantitative Marxian political economy is usually worked through by hand from the text. Kritik Systems turns it into calculators that show their working, so students and study groups can explore surplus value, the rate of profit and reproduction schemas with every step derived and cited.

What it does

• Calculators for surplus value, the rate of exploitation, organic composition of capital, the rate of profit and the tendency of the rate of profit to fall, reproduction schemas, prices of production, differential rent and more.
• Every result comes with a step-by-step derivation and cited notes, with fixtures taken from Marx's own worked examples in Capital.
• Saved scenarios, ordered sets, comparison views, charts, and JSON and CSV exports.
• Free to use with no account. A one-time purchase unlocks the Pro tools, and the licence also unlocks Pro reading guides on its sibling site, Praxis Primer.

How it's built

• A Next.js App Router app in TypeScript. The calculation engine is pure functions over readonly inputs, with no React, storage, network, clocks or randomness, so every formula is tested in isolation.
• Local-first: calculator inputs and scenarios stay in the browser in IndexedDB through Dexie and never leave it unless you export them.
• Supabase is used only for entitlements. Stripe Checkout and a webhook issue licence keys, which are stored as hashes and verified by both sites.
• The scope is deliberately narrow, with no user-generated public content and no moderation surface, so one person can maintain it in 6 to 12 hours a week.